1. Field of the Invention
The present invention relates in general to methods and systems in the field of software programming development, and more particularly to methods and systems used to debug software programs.
2. Description of the Related Art
One of the major inhibitors to developing parallel and distributed applications (e.g. client/server, peer-to-peer) is a lack of adequate debugging tools. To debug a parallel and distributed application, the tool should provide dbx-like functions that allow a user to monitor and control the execution of multiple programs with many threads of execution running on various machines and running on a variety of operating systems. The tool should also allow the user to display and modify the run-time states of all of those programs in a coherent fashion from a single user interface. The tool should also allow the user to display and modify the run-time states of all of those programs in such a manner that they all appear to be one program.
The state of the prior art is illustrated by Matsumoto (Japanese patent number JP 05-73367 entitled "Multiple Trace-Back Map Output System"). Matsumoto teaches the use of a PCB (parallel processing unit control table) to store the call relation between two parallel processing units when one parallel processing unit calls the other parallel processing unit. The PCB is also used to store the execution state of the calling parallel processing unit. In particular, Matsumoto teaches that one parallel processing unit when calling another parallel processing unit sets the call relation between its state and the parallel processing unit at the call destination in the PCB (parallel processing unit control table), and after the called parallel processing unit sets the execution state in the PCB, a processing is performed. If an abnormality occurs to one of the parallel processing units, the processing of all of the parallel processing units are interrupted, and then the execution states and call relation are outputted as the trace-back map by the parallel processing units by referring to the PCB. By this method, a debugging operation is made more efficient by sampling and displaying the trace-back map of the execution states of not only a parallel processing unit where an error occurs, but also all parallel process units in operation, and grasping the characteristic error, etc., at the time of a parallel processing abnormality having no reproducibility.
However, Matsumoto fails to recognize two problems resulting from the use of such a table of who-called-who relations (i.e., the processing unit control table). First, maintaining such a PCB table incurs a large overhead because a distributed program must be interrupted each time a call is made to record the new relation in the PCB, and again must be interrupted on return to delete the relation from the PCB. For "dbx-like" debuggers this overhead is substantial. Second, as the relations are recorded in the PCB in their order of occurrence, call relations from different distributed applications are intermixed in the PCB and impose an burden on a user interpreting the the PCB as a trace-back map of call relations.
In view of the above problems, there is a need for a method of, and system for, determining the call relations of a distributed program without the performance overhead of recording such relations in a table. Furthermore, in view of the above problems, there is a need for a method of, and system for, displaying the call relations of a distributed program in the same manner as those of a non-distributed program.